1. Field of the Invention
The present invention relates to a control valve for regulating an oil pressure supplied to respective flow passages in a lubricating oil supply apparatus of an engine, or more particularly a lubricating oil supply apparatus including a valve system supply flow passage for delivering lubricating oil to a cam journal and so on of a cylinder head, and a crankshaft system supply flow passage for delivering lubricating oil to a crankshaft, a connecting rod, and so on of a cylinder block.
2. Description of the Related Art
Attempts have been made in the past to vary an oil pressure of oil supplied from an oil pump in accordance with a rotation speed of an engine so that the oil is supplied at an optimum oil pressure for respective rotation speed regions. Attempts have also been made to lighten a load of the oil pump by regulating the oil pressure supplied to a valve system lubricating circuit and a crankshaft system lubricating circuit to an oil pressure required by each circuit.
To achieve such objects, an invention (to be referred to hereafter as “the invention according to Patent Document 1”) disclosed in Japanese Patent Application Publication No. 2009-264241 (Patent Document 1) has been proposed. The invention according to Patent Document 1 will be described briefly below. Reference symbols used in the description are identical to those used in Patent Document 1. First, oil is drawn from an oil pan 10 by an oil pump 12 and delivered to a first oil feeding path 16a and a second oil feeding path 16b. 
The first oil feeding path 16a is a path for supplying the oil mainly to a bearing portion 18 of a crankshaft, while the second oil feeding path 16b is a path for supplying the oil to a valve mechanism 20 and so on, for example. An oil pressure control valve 22 for controlling an amount of oil supplied to the bearing portion 18 of the crankshaft is disposed on the first oil feeding path 16a. The oil pressure control valve 22 is configured such that an output oil pressure thereof is controlled by a control unit 24.
The control unit 24 is controlled by an engine rotation speed sensor 26, an engine load sensor 28, an oil temperature sensor 30, and an oil pressure sensor 32. A relief valve 34 is provided to allow surplus oil pressure to escape into the oil pan 10 from a part of the oil path between the oil pump 12 and a filter 14 when the oil pressure exceeds a predetermined value. In this configuration, the oil pressure control valve 22 is controlled by the control unit 24.